The at or near room temperature detection of infrared radiation is becoming important in a wide range of applications in the civilian, industrial, medical, astronomical and military sectors. Infrared radiation can be detected by photon detectors and thermal detectors. However, excessive dark current levels can impede reliable detection of radiation by infrared detectors. Dark current is the background noise generated by thermal activity in a photodetector. In the semiconductor materials used in photodetectors, the dark current typically increases with temperature. Hence, the dark current effectively determines an operating temperature limit for a detector of well below room temperature. It is common for cooling temperatures to be at or below 77 degrees Kelvin (77 K). This can require a substantial cooling system to reduce detector temperatures to the necessary level.
One proposed solution to the foregoing limitations is the split-off infrared photodetector (SPIP) detector described in U.S. application Ser. No. 11/849,464 (“the '464 application”), entitled, “High Operating Temperature Split-Off Band Infrared Detector,” the contents of which are hereby incorporated herein by reference in their entirety. As described in more detail below, the SPIP detector described in the '464 application can comprise multiple periods of an emitter disposed between two barriers so as to form a heterojunction at each interface between the emitter and the first and second barriers, wherein the emitter is of a semiconductor material that is different from that of the barriers and has a split-off response to optical signals and a cutoff wavelength.
A limiting factor on the quantum efficiency, or gain, of the SPIP detector described in the '464 application, however, may be the trapping of carriers due to scattering between hot and cold carriers as they pass through the emitter layers of the detector. A need, therefore, exists for a technique to reduce this trapping and, as a result, improve the quantum efficiency of the IR detector, while maintaining the high operating temperature.